Extraction of crack closure component from threshold stress intensity

Abstract

An analytical procedure is described that connects crack opening stress intensity, Kop, with maximum stress intensity, Kmax, associated with threshold conditions under constant amplitude loading. The underlying theory is based on the experimental finding that closure-free intrinsic threshold stress intensity, ΔKth,i, is solely related to a certain computed near-tip residual stress, σ*. The proposed procedure enables extrapolation of ΔKth to lower values of maximum stress intensity, Kmax that cannot be reproduced by prevailing testing practice. It is demonstrated on experimental threshold data from a naval steel and a titanium alloy.